1. Field of the Invention
The present invention relates to a semiconductor device having a mark region and a source region, and particularly an SiC semiconductor device using silicon carbide, and a method of manufacturing the same.
2. Description of the Background Art
The breakdown electric field and the bandgap of silicon carbide are approximately ten times and three times greater than those of silicon, respectively. Accordingly, a power device using silicon carbide can operate at a higher temperature with a low resistance, as compared with a power device using silicon which is currently used. Particularly, a MOSFET and an IGBT using silicon carbide are quite prospective because a small loss occurs in a normal mode and at a time of switching, when compared with a MOSFET and an IGBT using silicon with the same breakdown voltage. Thus, various methods of manufacturing a MOSFET and an IGBT using silicon carbide have been proposed (for example, see Japanese Patent Application Laid-Open No. 2000-164525).
In the MOSFET using silicon carbide, a channel resistance accounts for a half of the on-resistance involved in a loss occurring at a time when current flows. The channel resistance is determined by a channel length Lch which depends on a positional relationship between a p-well region and a source region as shown in FIG. 1. If the channel length Lch varies due to mask misalignment occurring in a step of forming the p-well region and the source region, a chip may be broken by local current concentration in a chip face. Accordingly, how the channel length Lch can be accurately controlled is a significant problem.
In a conventional process of manufacturing a MOSFET using silicon carbide, at the beginning of a wafer process, a mark region is formed which serves as a reference for a mask alignment in a photomechanical process. Then, the mask alignment is performed based on the mark region, to form a p-well region. Moreover, the mask alignment is performed by using the mark region as a reference, to form an n-type source region. Furthermore, a well contact region is formed at the center of the source region. Then, in the same manner, the mask alignment is performed based on the mark region, to form an electrode structure.